Constitutive salicylic acid accumulation in pi4kIIIβ1β2 Arabidopsis plants stunts rosette but not root growth

Abstract

Summary Phospholipids have recently been found to be integral elements of hormone signalling pathways. An Arabidopsis thaliana double mutant in two type III phosphatidylinositol‐4‐kinases (PI4Ks), pi4kIIIβ1β2, displays a stunted rosette growth. The causal link between PI4K activity and growth is unknown. Using microarray analysis, quantitative reverse transcription polymerase chain reaction (RT‐qPCR) and multiple phytohormone analysis by LC‐MS we investigated the mechanism responsible for the pi4kIIIβ1β2 phenotype. The pi4kIIIβ1β2 mutant accumulated a high concentration of salicylic acid (SA), constitutively expressed SA marker genes including PR‐1, and was more resistant to Pseudomonas syringae. pi4kIIIβ1β2 was crossed with SA signalling mutants eds1 and npr1 and SA biosynthesis mutant sid2 and NahG. The dwarf phenotype of pi4kIIIβ1β2 rosettes was suppressed in all four triple mutants. Whereas eds1 pi4kIIIβ1β2, sid2 pi4kIIIβ1β2 and NahG pi4kIIIβ1β2 had similar amounts of SA as the wild‐type (WT), npr1pi4kIIIβ1β2 had more SA than pi4kIIIβ1β2 despite being less dwarfed. This indicates that PI4KIIIβ1 and PI4KIIIβ2 are genetically upstream of EDS1 and need functional SA biosynthesis and perception through NPR1 to express the dwarf phenotype. The slow root growth phenotype of pi4kIIIβ1β2 was not suppressed in any of the triple mutants. The pi4kIIIβ1β2 mutations together cause constitutive activation of SA signalling that is responsible for the dwarf rosette phenotype but not for the short root phenotype.

Arabidopsis PLC2 is involved in auxin‐modulated reproductive development

“…As one of the components in the plasma membrane, the PLC substrate PIP 2 has been reported to mediate attachment of many proteins to the plasma membrane (Kadamur and Ross, ). Phospholipid signaling in plants is integral for diverse biological processes including biosynthesis of phytohormones (Pokotylo et al ., ; Šašek et al ., ). Phosphatidylinositol‐4‐kinase, which catalyzes the phosphorylation of phosphoidylinositol to form phosphatidylinositol‐4‐phosphate, is involved in modulation of salicylic acid content in Arabidopsis (Šašek et al ., ).…”

“…Phospholipid signaling in plants is integral for diverse biological processes including biosynthesis of phytohormones (Pokotylo et al ., ; Šašek et al ., ). Phosphatidylinositol‐4‐kinase, which catalyzes the phosphorylation of phosphoidylinositol to form phosphatidylinositol‐4‐phosphate, is involved in modulation of salicylic acid content in Arabidopsis (Šašek et al ., ). However, there is no direct evidence to show whether molecules such as phospholipids, IP 3 and/or DAG participate in auxin metabolism.…”

Leptosphaeria maculans effector AvrLm4‐7 affects salicylic acid (SA) and ethylene (ET) signalling and hydrogen peroxide (H2O2) accumulation in Brassica napus

“…Discs surrounding the inoculation sites were cut by Harris Uni‐Core® (diameter, 6 mm) from at least six plants. Homogenization, total RNA extraction, treatment with DNA‐Free kit (Ambion, Austin, TX, USA) and reverse transcription of RNA to cDNA were performed as described previously (Šašek et al ., ). The reverse transcription‐quantitative polymerase chain reactions (RT‐qPCRs) were performed as described previously (Janda et al ., ).…”

Cytidinediphosphate‐diacylglycerol synthase 5 is required for phospholipid homeostasis and is negatively involved in hyperosmotic stress tolerance

“…PI‐3‐kinase (PI3K) and PI4K catalyze PI phosphorylation at the D3 and D4 positions of the inositol ring to produce PI3P and PI4P, respectively. Both PI3K and PI4K are important for plant growth (Lee et al ., ; Sašek et al ., ). To determine whether enhanced growth of the cds5 mutant is caused by PI itself or PI derivatives, wortmannin, an inhibitor of PI3K and PI4K, was supplied together with PI.…”